This invention relates to alkylation processes. In another aspect, the invention relates to alkylation of meta-xylene with alpha-olefinic compounds. In a further aspect, the invention relates to the production of alkyl aromatic compounds in high selectivity to the thermodynamically favored aromatic substitution isomer.
Friedel-Crafts, i.e., acid catalyzed alkylation of aromatics, is a well-known reaction. When aromatics are alkylated with an alkyl halide, substantial quantities of hydrogen halide are produced as a by-product of the reaction. Not only are the starting alkyl halides frequently costly and the formation of hydrogen halide as a by-product wasteful, in addition, the by-product hydrogen halide may create a handling and disposal problem due to its corrosive nature. In order to alleviate the above-mentioned problems, aromatics can be alkylated with olefinically unsaturated compounds frequently instead of with alkyl halides. However, prior art reactions of aromatic compounds with olefinically unsaturated compounds frequently suffer from poor selectivity to the preferred isomer of the alkylated aromatic product.
The kinetically favored aromatic substitution isomer, e.g., the kinetically preferred isomer, is predominantly produced when a mild alkylation catalyst and/or mild reaction conditions are used. When the thermodynamically favored aromatic substitution isomer, e.g. the thermodynamically preferred isomer, is the preferred isomer, the alkylation catalyst and reaction conditions required to produce the thermodynamically preferred isomer typically also favor other side reactions such as olefin isomerization, transalkylation and dialkylation.